The present invention relates to a grinding wheel feeder in a grinding machine, and more particularly to a grinding wheel feeder in a grinding machine having a sizing device for controlling the grinding wheel feeder to grind a workpiece to desired dimensions.
Numerically controlled grinding machines generally include a position register for storing data on the position of the grinding surface of a grinding wheel. When the stored data is accidentally erased upon power supply failure or emergency shutoff of the machine, it becomes impossible to locate the grinding surface of the grinding wheel.
To avoid such a drawback, it has been customary to measure and store, when the grinding wheel has an initial radius, the amount that a grinding wheel base moves from its fixed original position to a grinding start position at which the grinding surface of the grinding wheel is spaced a given distance from the axis of a workpiece to be ground, and then to accumulate data items on a compensation amount that the grinding wheel base is moved each time the grinding wheel is dressed. When the data on the position of the grinding surface of the grinding wheel is lost upon power supply failure or machine shutdown in case of emergency, the grinding wheel base is returned to the original position, and then advanced by an amount of movement which is equal to the sum of the initially stored amount of travel and the compensation amount of travel that have been accumulated. This allows the grinding surface of the grinding wheel to be positioned a desired distance from the axis of the workpiece after the data on the position of the grinding surface has been erased.
In practice, however, the actual radius of the grinding wheel varies to become progressively greater than theoretical dimension as the dressing tool in worn. At the time of positioning the grinding wheel base to the grinding start position after it has been returned to the original position, the position of the grinding surface is deviated from the grinding start position by a distance corresponding to the wear amount of the dressing tool. An undue increase in such a deviation results in the danger for the grinding wheel to interfere with the workpiece in grinding operation.